Convection-compensating centrifuge



March 27, 1951 c, F, HALL 2,546,186

CONVECTIOMCOMPENSATING GENTRIFUGE Filed March 11, 1947 3 Sheets-Sheet l MUM! March 427, 1951 c. F. HALL 2,546,186

CONVECTION-COMPENSATING CENTRIFUGE Filed March 11, 1947 5 Sheets-Sheet 2 5 Sheets-Sheet 5 iNvENToR @a/M if. M

C. F. HALL Y FIG.

March 27, 1951 Filed March ll, 1947 Patented Mar. 27, 1951 UNITED STATES PATENTOFFICE CNVECTON-COMPENSATNG CENTRIFUGE Charles F. Hall, Berkeley, Calil'.v

Application March 11, 1947, Serial No. 733,788

6 Claims. 1

My invention is a continuous now, cross current, convection-compensating centrifuge, in which an axial separation of fluid constituents of different mass is accomplished by means of adjacent oppcsitely flowing component axial currents having cross component currents which flow predominantly centrifugal across one axial current and flow predominantly centripetal across the opposite axial current. The axial separation is thus a function of centrifugal sedimentation velocities of the co-nstituents, is independent of maintaining a state of centrifugal enrichment between axial currents, and is maintained by cross currents of ample magnitude; consequently separation is not seriously defected by thermal or mechanical irregularities of operation. And since separation takes place in an axial direction the distance through which separation takes place may be extended to provide a large separation factor at high` resolving power; for separation of isotopes and other molecular or sub-molecular particles. Furthermore, the freedom from remixing defects allows use of a back wash or counter-current for continuous now separation of proteins, virus, and other colloidal particles suspended in ailuid.

This application relates to my prior copending patent applicationsfor Convection-Compensating Centrifuge, Serial No. 583,331, lled March 17, `1945 (now abandoned); Serial No. 624,761, iiled October 26, 1945, now abandoned; Serial No. 654,753, led March 15, 1946, now abandoned; and Serial No. 685,393, liled J`uly22, 1946. In addition thereto it shows a circuit diagram for two centrifuges employing a back wash current for separation of different colloidal particles of special 'value in biochemistry. And it shows .aI rotor having two concentric rings of series-paral-` lel connected nues; and a new type of centrifugal mixing and circulating system to feed the nues.

'Throughout the specincation and claims the term "axial or axially is used to denote a direction parallel or componently parallel to the axis of the centrifuge rotor; thus the expression axially inclined passages" designates passages that are inclined to provide a component ci fluid flow ina direction that is parallel 'to the axis;v

and the term axial separation designates a separation or enrichment of separable constituents that takes place in a direction that is paralilel to the axis. The term centripetal is used to denote a direction radially inward toward the axis of the rotor. The term centrifugal is used to denote adirection radially outward from the axis of the rotor. .And the term circumferentiaF' is used to denote a direction extending through 0f the 2 centrifugal force. The term "centripetal cross current is used to denote a radially inward component of current that crosses a component axial current. The terni centrifugal cross current used to denote a radiallyl outward component f current that crosses a component axial current.

The term axial current is used to denote con" ponent axial current. In the accompanying drawings: Fig. 1 is a horizontal longitudinal section of the device, sectioned on the line I, I, Fig. 2, Fig. 3, and Fig. 4.

Fig. 2 is a segment sectioned on the line 2, 2Fig. 1.

Fig. 3 is a segment sectioned on the line 3, 3, Fig.`1.` Fig. 4 is a segment sectioned on the line 4, 4, Fig. 1.

is a section on the line y8, 8, Fig. 5. And Fig. 9` is a schematic` circuit diagram for tw centrifuges connected for employing a back Wash curl.

rent separation. Fig. l0 is an enlarged, broken segment of the rotor sectioned on line 4, 4, Figs.

1, 11,- 12; it shows arrows to indicate the flow of iluid around each baille, especially showingcentrifugal and centripetal cross currents in the lues 24a, 24h, 24e. Fig. l1 is a broken section through the group of ilues 24a, 24h, 24e, taken on a circumferential surface through the rotor on the line II, II, Fig. 10, and showing the baffles sectioned on the line 1, l, Fig. 5, and midlengths of the wires 2l are broken away; it shows arrcws t6 indicate the flow of iluid around each baille, especially showing axial currents. Fig. 12 is a section on the line l2, l2, Fig. 10; it snows arrows' to indicate a resultant current on one side of' a baffle. In both Figs. l1 and`12 the short arrows indicate currents in the vicinity of a radially outer edge of a baille; and the long arrows indicate currl stationary disks 4, to the smooth surfaced sleeve gaskets 5, to the stationary vanes 6, and to the.

stationary radial extensiontubes l.

The rotor is driven by a gear or turbine drive wheel 8, and it revolves on the bearings 9. Each of the two rotor hub disks I0 are provided withvv Each hub disk is hermetically cemented to a partition disk I2 internal radial channels II.

hermetically cemented to a radially channelled disk I3 provided with radial channels I4. The outer end of each radial channel II is connected tothe outer end of each corresponding radial channel I4 by a hole 33 and at the: center the channels are connected through a hole 36 in the center of each disk I2, Figs. 1 and 2'. At one end ofthe rotor the inlet duct 30 connects with ,1.

Similar numerals refer to similar parts.

radial channels and the outlet duct 34 con nects through an extension tube 'l with radial channels Hl. At the other end of the rotor the inlet duct 3| connects with radial channels and the outlet duct 32 connects through an extension tube 'l' with radial channels M. At one end of the rotor, the disk i3 is hermetically cemented to the electrically insulative non-breakable glass disk I5 which is hermetically cemented to the rotor mid-piece I6; and at the other end of the rotor the disk lli is hermetically cemented to the rotor mid-piece. The facings between the rotor disks must be smooth and the hermetical seals of cement must be thin so as not to be dislodged by centrifugal force. All of the rotor disks are bolted to the rotor mid-piece by means of the bolts il. The bolts at one end of the rotor are electrically insulated by the non-breakable glass sleeves I8.

The annular channels I9 are lled with a suitableV liquid tov provide centrifugal' liquid seals around the annular fianges of the sleeve gaskets 5; they are filled by way of screw plugged holes not shown.

Heating at the bearings is roughly equalized, to provide a fairly uniform temperature throughout the rotor mid-length, by a cooling fluid whichis ejected onto the rotor hub disks by way of the stationary jets 20.

The rotor mid-piece is longitudinally perforated to provide axial flues through which con-v stituents of the fluid content are axially separated. Any desired odd number of the axial flues may be vconnected in series by means of the plugs 2| and the connecting holes 22; thereby providing a single continuous series flue having an effective length which is some odd number of times greater than the effective midlength of the rotor. Or if the rotor is long enough the plugs 2| and the holes 22 may be omitted to provide a parallel connection of ues.

Cemented in the open ends of each group of series connected nues are the diffusion plugs 23; which may each be made of tightly packed liber glass cloth cemented in a peripherial plastic sleeve. They should be made so that their length and open area limits diiusion in each nue to approximately that of the volume of fluid being separated through each ue. In this way, undesiredinterconvection currents, between parallel connected groups of nues, are kept negligibly small. If the flues are all connected in series then the diffusion plugs 23 may be omitted. As shown in the drawings the iiues are connected in seriesparallel in groups of three series connected nues 24a., 24h, and 24e.

Withineach flue and passing through or around a radially outer and a radially inner part of each baille are rows of closely spaced passages 25; said passages being in full or in part axially inclined todirect cross 4current circulation in a componently axial direction so as to produce axial currents, see Figs. l, 4, 5, 6, 7, 8, 10, 11, l2. The passages may be adjacent to the edges or intermediate to the edges of each baffle or they may be part of any member within a flue, but they must be separated by a radial distance in the direction of centrifugal force, they must be closely spaced inthe axial direction, and they must be at least in part axially inclined. The passages may be rectangular holes as shown or they may be molded in the shape of converging nozzles. In the ends of each baille there are diagonally opposite openings 31 through which the axial currentsA circulate. The series connecting nues 24h 4 have plugs 2| at both ends and the direction of separation is reversed therein; hence the position of, as shown in Fig. 4, the diagonally opposite openings 31 is transposed in the lues 24D.

Each baille is molded, or otherwise attached to a cross element so that the whole baie member has the shape of a T, as shown; and the whole member should be made of glass or some other suitable heat insulative material. Each baille member carries an electrically heated metal strip or Wire 2l both ends of which are electrically connected to the disks |2 and thus electrically connected through the stationary slip rings 28 and through the diagrammatically shown electrical connections 38 to `a controlled source of electricity. If gases or vapors at reduced pressure are to be separated, then the Wires 2 should be disconnected and broken away from the disk l2 at the end of the rotor mid-piece which is not electrically insulated therefrom, and a high enough voltage should be applied to the wires to produce a glow discharge throughout the length of each flue; thus directly heating the gas on one side of each baille.

By means of the cooling jets 20 and the heat* ing wires 2l, heat distribution is controlled so that circumferential temperature gradients exceed axial temperature gradients throughout the fluid content in the mid-length of each ilue.

ADue to centrifugal head of pressure and circumferential tempera-ture gradients, currents now around each baii'ie and through the axially inclined passages 26, see Figs. 10, 11, l2. The open area of the passages 25, through which the currents flow, is shown in Figs. l, 6, 12. For a full length ue, for example in a rotor three or four feet long, the total open area of all of the passages 26 is greater than the cross sectional area of a ue as seen in Figs. 4 and 10; also the axial current velocity as produced by the axial incline of the passages 26 is less than the velocity through the passages; thus the volume of luid circulating as cross currents exceeds the volume of fluid =circulating as axial currents and a state of axial separation is maintained.

.Furthermore the open area of the passages 26 is less than the cross sectional area of a flue as seen in the sectional view, Fig. 1l; thus the velocity of the cross currents through this section is less than the velocity of the currents through the passages and consequently the velocity of the axial currents, as a function of the currentsl through the passages, is greater than the velocity of the cross currents and so an amplied separation factor is attained.

F tion ofseparation. So for each transposition in a series connection of iiues: the inclination of the passages, toward their heated wire, is reversed. But for a parallel connection of lines: the passages must always have the same inclination toward their heated wire.

To provide the most effective centrifugal temi perature gradient, for centrifugal heat dissipation,'the` electrically heated wires. in the central ring of ues shouldY be heated to a higher temperature thanv the electrically heated wiresin ltl'icouter ring of flues.

j Considering the flow of fluid in flue 24e, Figs. l, 4,'10, `1l, 12: due to centrifugal head of pressure in conjunction with circumferential temperature gradients, fluid passes from the unheated side of the' flue to the heated side through axially inclined passages 26 along the radially outer edges of a baffle 25, and it passes from the heated side to,v the unheated side through axially inclined passages 26 along the radially inner edge of the baille. In passing through the axially inclined passages it is given an axial circulation; thus f or flue 24e, as seen in Fig. ll, there is a downward axialcurrent on the unheated side and an upward axial current on the heated side; and as seen in Fig. 10, there is a centrifugal cross current on the same side as the downward axial current` and a centripetal cross current on the same side as the upward axial current. Within the fluid are both' heavy and light weight separable constituents which are affected by centrifugal force and for the illustration given herein it is considered that the heavier constituents have faster centrifugal sedimentation velocities than the lighter constituents. For separation of constituents such as molecules or colloidal particles the velocity of the cross currents is greater than the centrifugal sedimentation velocities of the constituents; and so the cross currents carry the constituents around the baille. Due to the differences in centrifugal sedimentation velocities,

the vlighter constituents, as carried in the centrifugal cross current, travel slower than the heavier constituents and thus the lighter constituents are enriched within the unheated axial current and are .displaced and axially enriched in the direction of said unheated axial current. But in the centripetal cross current the heavier constituents travel slower than the lighter constituents and thus the heavier constituents are enriched within the heated axial current and are displaced and axially enriched in the direction of said heated axial current. The axial enrichment is dependent upon averaged differences in the summation of the centrifugal and centripetal cross currents and sedimentation velocities as circumferentially maintained by the baille in each flue. It is not dependent upon maintaining a state of centrifugal enrichment and so it is not adversely affected by centrifugal and centripetal circulation of the fluid which destroys or defects the centrifugal enrichment necessary in other types of centrifuges.

, The flues 24a, 24D, 240,. are connected in series by means of the holes 22; the .direction of separation is 'reversed in the ilue 24h; and so from this group of seriesconnected ilues the axial enrichment of lighter constituents diffuses through the porous plug 23 in the end .of the flue 24e and out of.. the flue intothe channels at one end of the` centrifuge, and the axial enrichment of heavier constituentsdiffuses through the porous plug 23 in the end of the flue 24a and out of the flue into the channels |I at the opposite end of is-fed','asa back wash current,l through the duct' 30. By way of the two ducts 3| and 32, the fluid mixture is continuously circulated and mixed, between the centrifuges A and B, by means of the difference in centrifugal pressures established by the stationary radial extensiontubes 7. In-the,

end compartments of both centrifugesv the stationary vanes 6 serve to produce `a dierence in centrifugal pressure which circulates the mixture' through the radial channels and i4; thus providing centrifugal mixing and uniformly distributlet duct 34 and the lighter particles may beV The cen trifuge A is to separate the heavier constituents from the mixture circulating in the ducts 3| and drawn off from the outlet duct 35.

372 and the centrifuge B is to separate the lighter constituents from the mixture circulating in the ducts 3| and 32. At one end of each of the two centrifuges the duct 3| connects to the duct 29 and connects the outlet channels of centrifuge B to the inlet channels of centrifuge A; and the duct 32 connects the outlet channels of centrifuge A to the inlet channels of centrifuge B. At the opposite end of centrifuge A the duct ,3Q connects to the inlet channels of centrifuge A, and duct 3.4 connects to the outlet channels of centrifuge A. At the opposite end of centrifuge B the duct 35 connects to the outlet channels of centrifuge B, and the duct connecting to the inlet channels, of centrifuge B, is plugged off or omitted.

The separation velocity of the particles variesA directly as their difference in molecular weights,

that is directly as the resolving power, and sepa-- ration is not dependent upon maintaining a critical state of centrifugal enrichment, hence control is not excessively critical even for high resolving powers.

For separation of a mixture of fluids it is not necessary to employ the back wash current principle of separation; although the holdover time before starting to draw off minority constituents may be reduced if this principle is employed.

There are a number of modifications of my invention. For instance the flues may be extended circumferentially, spirally, helically, or on a conical incline. But such modifications do not depart from the principles illustrated in the drawings and specification and. set forth in the following claims.

` I claim:

v l. n a centrifuge a rotor comprising a cylin .der perforated by a number of axial fiues through which a fluid and separable constituents are circulated, a baille circumferentially dividing each flue,

in each baille a.multiplicity of closely spacedy axially inclined passages passing through auradially outer part of the baille and a corresponding multiplicity of closely spaced axially inclined passages passing through a radially inner part of the baille, on one side of each baille an axially extending thermal element producing convec# tional circulation of uid through the axially inclined passages said inclined passages-being so".

positioned that said circulation producesoppositely directed component axial currents on circumferentially opposite sides of each baille and" produces component cross currents which flowv predominantly centrifugal across one component axial current and ilow predominantly centripetal a'cross the oppositely directed component axial current, at opposite ends of the rotor a number of radial channels connecting the ends of the flues to stationary inlet and outlet `ducts and stationary vanes and stationary radial extension tubes circulating the fluid through the radial channels and through the ducts, bearings to support the rotor and means to cool the bearings and minimize axial temperature gradients through the rotor, all combining to provide a maintained axially ampliiied enrichment of constituents maintained by cross currents and dependent upon a maintained circumferential enrichment of constituents as maintained by the baille within each flue.

2. In a centrifuge the combination of axially extending flues circumferentially divided by axially and radially extending baffles in which a multiplicity of closely spaced axially inclined passages pass through radially outer and radially inner portions of the baffles, means for circulating fluid through said axially inclined passages said passages being so positioned as to provide centrifugal and centripetal cross currents and axial currents for axial separation of constituents within said flues, means for supplying fluid to said ilues and means for withdrawing iluid from said flues adjacent the ends thereof.

3. In a centrifuge a rotor comprising a cylinder perforated by a number of axial flues through which a fluid and separable constituents are circulated, a baffle circumferentially dividing each flue, in each baille a multiplicity of closely spaced axially inclined passages passing through a radially outer part of the baille and a corresponding multiplicity of closely spaced axially inclined passages passing through a radially inner part of the baille, electrically insulated therefrom and supported by the radially outer wall of each ilue and on one side of each baffle an axially extending electrically heated strip electrically connected to slip-rings at the ends of the rotor and providing an electric thermal element in each flue, said passages being so positioned that said thermal element produces radial circulation about said baille and axial circulation in opposite directions on opposite sides of baffles, thereby producing enrichment of said constituents axially of said flues, means for supplying fluid to said flues, and means for withdrawing fluid from said flues adjacent the ends thereof.

4. In a centrifuge, in combination, a rotor comprising a cylinder perforated by a number of axial flues through which a fluid and separable constituents are circulated, a baille circumferentially dividing each flue, in each baille a multiplicity of closely spaced axially inclined passages passing through a radially outer part of the baille and a corresponding multiplicity of closely spaced axially inclined passages passing through a radially inner part of the baffle, on one side of each baille an axially extended thermal element, at opposite ends of the ilues holes and plugs to connect groups of flues in series and in each alternate flue of each series connected group a transposed thermal element to provide a reversal of separatio-n within said alternate flue so that separation Within each series group of ilues is directed back and forth along the axial length of the rotor to extend the' distance through which constituents l are separated to improve purification of the separation, diffusion plugs in the ends of each group of series connected flues to prevent excessive circulation between these groups of ilues and to'v thus allow a parallel connection of groups of ues to increase volume of separation as connected through radial channels and inlet and outlety 5. In a centrifuge rotor through which a fluid and separable constituents circulate, radially extended baflles to maintain adjacent oppositely flowing currents of fluid on circumferentially opposite sides of the baffles, a multiplicity of closely spaced passages located at radially outer and radially inner positions through which circulation of fluid passes the bailles, and an axial inclination of the passages to direct the currents in ccmponently opposite axial directions on circumferentially opposite sides of the bailles, thermal elements being so positioned as to produce centrifugal and centripetal cross currents and to establish the circulation of fluid, at opposite ends of the centrifuge rotor channels to collect axial enrichment of the separable constituents and inlet and outlet ducts connected thereto.

6. A centrifuge circuit comprising a centrifuge A for separating heavier constituents from a fluid mixture and a centrifuge B for separating lighter constituents from a fluid mixture, both the centrifuges being of a structure as recited in claim l; connecting to channels in one end of centrifuge A, a valve and inlet duct for fluid unmixed with constituents and a valve and outlet duct for fluid mixed with an enrichment of heavier constituents; connecting to channels in the opposite endV of centrifuge A and connecting to channels in one end of centrifuge B and connecting to a Y connection duct and valve through which both heavier and lighter constituents are fed to thev circuit, an outlet duct of centrifuge A connected to an inlet duct of centrifuge B and an inlet duct of centrifuge A connected to an outlet duct of centrifuge B; connecting to channels in the opposite end of centrifuge B a Valve and outlet duct for iluid mixed with an enrichment of lighter constituents.

CHARLES F. HALL.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date Re.21,168 Coutor Aug. l, 1939 507,442 Lentsch Oct. 24, 1893 895,173 Ecaubert Aug. 4, 1908 1,061,656 Black May 13, 1913 1,126,247 Mason Jan. 26, 1915 1,525,808 Hall Feb. 10, 1925 1,700,928 Fawkes Feb. 5, 1929 2,114,497 Kelling Apr. 19, 1938` 2,176,982 Thayer Oct. 24, 1939 2,223,999 Miller Dec. 3, 1940 2,258,594 Brewer Oct. 14, 1941 2,286,157 Podbielniak June 4, 1942 2,313,540 Hall Mar. 9, 1943 2,394,357 Beese Feb. 5, 1946 2,422,882 Bramley June 24, 1947 OTHER REFERENCES A general Account of the Development of Methods of Using Atomic Energy for Military Purposes-Smith, 1945. (Copy available in Div. 25, U. S. Patent Oillce.) 

